The product such as tires or conveyor belts using the rubber/steel-wire composite usually uses a band-shaped unvulcanized-rubber/steel-wire composite, in which a plurality of steel wires are arranged in parallel and buried in unvulcanized rubber, as an intermediate material.
The steel wires to be used for those products are high-carbon steel wires containing carbon of 0.6 to 1.1 wt. % and have to be highly drawn for manifesting their high strength. In order to improve the adhesiveness between the steel wires and the rubber and to enhance the lubricity at the drawing time, on the other hand, it is ordinary to plate the steel wires with brass or zinc before the drawing treatment.
In the prior art, a number of steps have passed before the aforementioned steel wires are worked to a composite with the unvulcanized rubber. Specifically, the drawn steel wires are once taken up on bobbins so that a plurality of wires are twisted to a steel cord by a twister. This steel cord is taken with a predetermined length on a bobbin and is commercially available.
The rubber manufacturer produces a primary composite composed of the unvulcanized rubber and the steel cords, by purchasing a plurality of coils of steel cords, by setting the plurality of coils on a cord supplier called the “creel stand”, by feeding the plurality of cords while arraying them to a rubber coater through guides or guide rolls. At this time, the band-shaped primary composites are taken up through a parting sheet of polyethylene or the like between the layers so that they are prevented from adhering with each other.
On the other hand, a secondary composite having an intrinsic width and cord angle is prepared by cutting the primary composite at a predetermined angle to a predetermined size and by jointing the end faces of the cuts to each other. At this time, the band-shaped secondary composites are taken up through a parting sheet of polyethylene or the like between the layers so that they are prevented from adhering with each other. Then, the secondary composite thus taken up is conveyed to an apparatus for shaping the tires or conveyor belts so that it is formed into unvulcanized products.
Thus, the method of the prior art is required to have many steps till the unvulcanized-rubber/steel-cord composite is produced from the starting materials, and is accompanied by a resultant problem the working cost is seriously raised. In order to lower this working cost, it is conceivable to speed up the drawing work of the steel wires. If the steel wires are drawn at a high drawing percentage and at a high speed, however, there arises a disadvantage that the steel wires drops in strength and in fatigue resistance.
On the other hand, the drawn steel wires are coated, just after drawn, with a plating layer but are oxidized on their surfaces if left as they are. There arises another problem that the adhesiveness between the wires and the rubber is degraded. In the prior art, the oxidation is prevented by adjusting the humidity of the place for stocking the steel cords, but this stocking management leads to a rise in the working cost.
An object of the present invention is to provide a method and apparatus for producing an unvulcanized-rubber/steel-wire composite, which can reduce the working cost drastically and can improve the fatigue resistance of the steel wires and the adhesiveness between the wires and the rubber.